Traditional Chinese medicine refers to the medicinal materials and clinical application of such materials in the framework of the theoretical and empirical parameters circumscribed by the Chinese people in the last 2-3 millennia. This medical system and many of the medicinal materials have spread to and have been adopted by other Oriental countries such as Japan and Korea and evolved into Oriental medicine in those countries. As a result, traditional Chinese medicine should not be limited to only the herbs and other natural products used in Chinese medicine, but also to Oriental medicine. Traditional Chinese medicine currently in mainland China also covers the practice and medicinal materials used by Tibetan, Mongolian and other ethnic minorities.
The herbs and other natural products (animals and minerals) used in Chinese medicine have been recorded in a) classical herbals, e.g. Bencao Gangmu {character pullout} and Bencao Gangmu Shiyi {character pullout} the two together contain about 2,500 items; b) pharmacopoeia, e.g. Pharmacopoeia of the People's Republic of China {character pullout} which contains some 600 items; and c) treaties, e.g. Encyclopedia of Chinese Materia Medica Zhongyao Dacidian {character pullout} , which contains 5,767 items.
Traditionally the authentication of Chinese herbs relied upon morphological and histological inspection. In many cases, such as in the authentication of different ginseng species, and in the authentication of Acorus species, this method is unreliable. An effective program of authentication of Chinese herbs is essential and central issue in the healthy development of the herbal industry. It provides a necessary protection for consumers, minimises unfair business competition and prevents the health hazard of many adulterants.
In plant, animals and insect nuclear genomes, genes for ribosomal RNA (rDNA) are normally clustered in an array of multiple tandemly repeated copies of the cistron of 18S-ITS1-5.8S-ITS2-28S (Hillis, D. M and Dixon, M. T., 1991, The Quarterly Review of Biology, 66: 411-453). The sequence separates the 18S and 5.8S rRNA genes is designated as ITS1 (Internal Transcribed Spacer 1) and the sequence between 5.8S and 28S is designated as ITS2. The coding regions of the three rDNA genes are highly conserved, whereas the sequence homology within the ITS1 and ITS2 regions are lower across the plant kingdom. Furthermore within a given individual organism or species, the rDNA sequence is usually very similar due to the homogenization of the sequence by gene conversion and crossing over. This invention takes advantage of these features of plant rDNA, and use PCR to amplify the DNA of ITS1-5.8S-ITS2 regions with the conserved DNA sequences flanking to the regions as primers, and explores the DNA polymorphism in different plant species within the ITS1-5.8S-ITS2 region as a mean of authentication.
The roots of Panax quinquefolius (American Ginseng) and P. ginseng (Oriental ginseng) are important herbal medicinal materials widely applied in the Orient as tonic, prophylactic and anti-aging agents. In recent years the American ginseng, cultivated mainly in Wisconsin, USA, and British Columbia and Ontario, Canada, enjoys increasing popularity as a health food in Western countries. The ginseng trade is a big industry, in 1993 Hong Kong imports more than HK$1,500 million worthy of American and Oriental ginsengs. The retail price of cultivated American ginseng is usually much more expensive than that of cultivated Oriental ginseng produced in China, and that prompts wild-spread practice of disguising Orient ginseng as American ginseng by dishonest merchants. Tremendous financial incentive is also responsible for the imitation or adulteration of ginsengs with some herbal products including several poisonous plants that bear morphological similarity with ginsengs. The two ginsengs also have different medical values and potency.
Both American and Oriental ginsengs, together with several important Chinese medicines including Sanchi (P. notoginseng), belong to the genus of Panax in the family of Araliaceae. American ginseng and Oriental ginseng have similar morphological appearance. Furthermore many commercial ginseng products exist in the forms of powder or shredded slice, rendering their authentication by morphological and histological methods difficult and unpractical. In recent years, techniques have been developed to authenticate ginseng samples by examination of their ginsenoside profiles (Lang, Z., Lou, W S. and But, P P H, 1993, J. Clin. Pharm. Sci., 2:133-143). However, the application of chemical analysis may be limited as the amount of ginsenosides are significantly affected by many environmental factors such as the storage condition, the freshness of the products and the different post-harvest processing. In addition, the chemical method demands large quantity of materials for proper analysis.